We propose to investigate the molecular mechanisms by which the antibiotic alamethicin forms voltage-gated pores in artificial membranes. Among the few molecules which confer excitability to artificial lipid bilayers, alamethicin is particularly attractive because it is fairly well understood and amenable to chemical modifications. Conductance measurements of alamethicin-doped black lipid membranes by themselves are insufficient to distinguish among the various models for pore formation. We propose to use chemically modified fluorescent and structural analogs of alamethicin to answer dynamic and structural questions about the voltage dependence of pore formation. Sensitive fluorescent techniques will be coupled with electrical measurements in single lipid bilayers. We have developed, and will continue to improve, sensitive techniques to measure and analyze the conductance of single pores and to detect fluorescence signals from individual membranes. We propose to use these techniques to obtain quantitative information about the ionic selectivity of the alamethicin pores and to characterize in detail the interactions of the analogs in the formation of pores. We believe that these approaches will narrow down significantly the possible models. The techniques we propose to develop will also be of significance in studying pores which are extracted from excitable biological membranes and reconstituted into artificial lipid bilayers.